Comment spam is the harsh reality and every green behind the ears,
enthusiastic, unprepared blogger will be staggered by the sheer volume
they receive of it. WordPress can help, but you need to mentally prepare
yourself for the hard fact that more than 99% of the comments you will receive is going to be spam. If you leave the issue unattended, the spam can quite literally overtake your site database and get you permanently banned from search engine index.

The first thing on your to-do list should be to prepare your website
admin (backend) to help you deal with such massive amounts of bull.
That’s where WordPress bloggers have an advantage. As much spam there
is, there are quite a handful of powerful solutions, available free or
for pocket-change-cost, to help stop and/or manage spam influx on your
website.

1. Akismet

Shipped free of cost with every WordPress install, Akismet
is a staple because it’s WordPress through and through. This is the
prima donna of all anti spam plugins available for WordPress.
Developed by Automattic, Akismet is pretty damn powerful. The
enterprise grade spam prevention (and management) features are off the
charts, some of which include a self-learning spam detection algorithm
(notes your ‘comments marked as spam’ and uses it for automatic spam
marking in future). The plugin also lets you put your comments on
Akismet server (where they undergo spam checks by the aforementioned
algorithm). Comments that pass the inspection are published on your
site’s front end, while the rest are marked spam and eventually deleted.
All the comments (spam or genuine) are maintained in logs that you can
check at your leisure.
Akismet comes with up to 50k spam checks per month, only for non
profits and personal blogs. Commercial websites can get the API key by
subscribing at $5/month charge – a reasonable cost which is absolutely
worth it.

2. WP-SpamShield Anti-Spam

WP-SpamShield Anti-Spam is featured right on top in ‘anti-spam
plugin’ search results on WordPress.org Plugin Repository. It deserves
the spot.
The plugin is absolutely free of cost and efficient to the last
degree. It can tackle spam in comments, registration/ sign up forms, trackbacks and pingbacks,
etc. It can track and identify incessant spammers (based on IP) and let
you blacklist the troublemakers to protect your site’s database from
spam. It even has a JavaScript (cookie authentication) layer to help prevent spam from bots.
The plugin has nothing to do with Captcha or those lame ‘prove you
are a human’ questions/ tick boxes. It automatically blocks proxy server
users and supports every major WordPress form plugin.
It’s a smart plugin that costs nothing.

3. Anti-Spam Bee

With over a million active installs and counting and a glowing letter of recommendation from WordPress co-founder Matt Mullenweg himself, you can be sure you’re not wrong with Anti-spam Bee.
This plugin is free for all and super smart. It can take care of IP blacklisting (comment blocking), trackback validation, database optimization (a feature many people get by downloading a separate plugin like WP Sweep), and more. It shows you detailed monthly stats and spam activities in your admin dashboard and lets you ‘create’ your own spam detection algorithm by selecting certain indicators based on your knowledge of your user base.
Told you it’s an intelligent little beast. It’s also completely
devoid of any annoying ads and complies with data privacy standards
(Europe), which is another layer of icing on the freaking cake of
awesomeness.

4. CleanTalk

This is one of the best premium online (cloud based) spam protection services available for WordPress.
CleanTalk prevents comment spam, registration/ sign up form spam,
and trackback spam and uses smart algorithms to detect spam within
‘genuine’ looking comments uploaded on the Clean Talk cloud. You also
get detailed statistics and comments log, along with automatic
moderation (spam detection) activity and history.
The service is free for a 2 week trial period, after which you can
continue to use and scale up the service with a measly $8/yr charges per
domain.

5. WordPress Zero Spam

This is one of the simplest spam prevention plugins.
WordPress Zero Spam works by blocking comments from users who don’t
have JavaScript enabled on the browsers. It works with client and server
side JS validation, which works to prevent most bots from spamming your
comments section.
It’s free of cost and superbly compatible with almost every major
(and trusted) WordPress plugin (except Jetpack) and a whole variety of
contact form plugins. Keep in mind that while it’s great against bots,
it’s largely ineffectual against humans.

6. Growmap Anti Spambot Plugin (GASP)

Developers who hate the spambots with the intensity of thousand suns created Growmap Anti Spambot Plugin.
The GASP is simple: It adds a checkbox to your comment form asking
your site visitors to check it to prove they are human. Since the box is
generated using JavaScript on user’s own browsers, most bots won’t see
it and fool the plugin.
It’s lightweight, effective, and free.

7. Stop Spammers Spam Prevention

This is a Jack-of-all-trades, multitasking plugin that can take a load off your head while dealing with comment spam.
Stop Spammers Spam Prevention blocks comment spam, sign up form spam,
trackbacks, and contact form spam by passing them through a set of
powerful and thorough algorithms. The plugin can block IPs from over 100
countries. It also gives a warning (Request Denied) page to the spammer (human and otherwise) promptly followed by a captcha: this second layer prevents spambots.

Conclusion
Here you are: the top 7 tools to protect your WordPress site from spam
and prevent it from accumulating in your server and database in the
first place. Keep your WordPress website clean and well maintained, and
install one of these as soon as you get your website up and running.